Data from: Asymmetric oceanographic processes mediate connectivity and population genetic structure as revealed by RADseq in a highly dispersive marine invertebrate (Parastichopus californicus)

Marine populations are typically characterized by weak genetic differentiation due to the potential for long-distance dispersal favouring high levels of gene flow. However, strong directional advection of water masses or retentive hydrodynamic forces can influence the degree of genetic exchange among marine populations. To determine the oceanographic drivers of genetic structure in a highly dispersive marine invertebrate, the giant California sea cucumber (Parastichopus californicus), we first tested for the presence of genetic discontinuities along the coast of North America in the northeastern Pacific Ocean. Then, we tested two hypotheses regarding spatial processes influencing population structure: (i) isolation-by-distance (IBD: genetic structure is explained by geographic distance), and (ii) isolation-by-resistance (IBR: genetic structure is driven by ocean circulation). Using RADseq, we genotyped 717 individuals from 24 sampling locations across 2,719 neutral SNPs to assess the degree of population differentiation, and integrated estimates of genetic variation with inferred connectivity probabilities from a biophysical model of larval dispersal mediated by ocean currents. We identified two clusters separating north and south regions, as well as significant, albeit weak, substructure within regions (FST = 0.002, p = 0.001). After modeling the asymmetric nature of ocean currents, we demonstrated that local oceanography (IBR) was a better predictor of genetic variation (R2 = 0.48) than geographic distance (IBD) (R2 = 0.17) and directional processes played an important role in shaping fine-scale structure. Our study contributes to the growing body of literature identifying significant population structure in marine systems and has important implications for the spatial management of P. californicus and other exploited marine species.海洋种群通常表现出较弱的遗传分化，这是因为其具备长距离扩散的潜力，从而促进了高水平的基因交流。然而，强劲的水团平流或滞留性水动力作用力，会影响海洋种群间的基因交流程度。为探究高度扩散性海洋无脊椎动物——加利福尼亚巨海参（*Parastichopus californicus*）遗传结构的海洋学驱动因子，我们首先在东北太平洋的北美沿岸海域检测了遗传不连续性的存在情况。随后，我们针对影响种群结构的空间过程提出了两个检验假说：（1）距离隔离（isolation-by-distance, IBD：遗传结构由地理距离解释）；（2）阻力隔离（isolation-by-resistance, IBR：遗传结构由海洋环流驱动）。本研究利用RADseq技术，对分布于24个采样点的717个个体进行基因分型，共获得2719个中性单核苷酸多态性（Single Nucleotide Polymorphism, SNP）位点，以评估种群分化程度；同时将遗传变异评估结果与由洋流介导的幼体扩散生物物理模型所推断的连通概率进行整合。本研究鉴定出两个区分南北区域的遗传簇，同时在区域内检测到显著但较弱的亚结构（FST=0.002，p=0.001）。在对洋流的非对称性进行建模后，我们证实相较于地理距离（IBD，R²=0.17），局地海洋环境（IBR，R²=0.48）能更好地预测遗传变异，且定向过程在塑造精细尺度种群结构中发挥了重要作用。本研究丰富了海洋系统中显著种群结构相关的日益增长的文献体系，同时对于加利福尼亚巨海参（*Parastichopus californicus*）及其他被开发利用的海洋物种的空间管理具有重要参考价值。